@SM Scorx Come to think of it, there are three seiyuu in which are in the credits that aren't assigned roles in this game.

Kanehira Yamamoto
Taira Kikumoto
Shohei Yamaguchi

I'm sure three of those seiyuu did Nemesis if anything, but truth be told, my eyes are either on Kanehira Yamamoto or Taira Kikumoto as the voice of Nemesis if his voice files are in the Japanese files instead of English.

To be honest, I'm not sure if Nemesis sounds like either one of the two (or three if Shohei Yamaguchi is a choice) at all...

@Mikel I would guess one of them must be it then. I asked Chris Cox on Facebook, and he confirmed that he's not Nemesis, nor does he knows who it is, but the entire cast of English VAs recorded together.